None of the turn signals work. The four ways and running lights work. The fuse is good, I just replaced the left mirror assembly and plugged it in. I have even tried unplugging and no change. I think it has something to do with the switch but not sure or how to test it and take off the handlebar. Any suggestions appreciated.
Thanks
Over 60

I had a similar problem on the GL1500. If the 1800 is similar the 4 way flasher relay and turn signal relay are interchangeable. If you can locate them, and they are the same, you could swap them to see if the problem moves. On my bike the problem was the turn signal cancelling switch located below the triple tree.
Hopefully someone else can give you a better answer.

What is the triple tree? I did find the four way relay under the seat. Is the turn signal relay under the seat also? I did remove the turn signal switch and clean that out. Still nothing. There is a relay behind the speedometer that I am trying to rule out without going back there.
Any suggestions appreciated.
Fred

The triple tree is where the handlebars mount to the steering hread.
I don't know the GL1800 well enough to know where the relays are. If the turn signal is under the seat the flasher should be to. Activate it and feel which one is clicking.

/ Part no. 2
TURN SIGNAL RELAY
Remove the meter panel visor (page 3-13 of Service
Manual).
Turn the ignition switch to OFF and disconnect the
turn signal relay connector (black) from the turn
signal relay.
Check the connector for loose contacts or corroded
terminals.
POWER INPUT LINE INSPECTION
Turn the ignition switch to ON or ACC.
Measure the voltage between the Light green/black
wire terminal (+) of the turn signal relay connector
(black) and ground (–).
There should be battery voltage.
FUNCTION CHECK
Connect the turn signal relay connector (black).
Ground the Blue/green wire terminal of the turn
signal relay connector (black) with a jumper wire.
Turn the ignition switch to ON or ACC and operate
the turn signal switch.
The turn signal lights should blink.

No, you're posting a link to something only you have access to. You're going to have to save the picture and upload it as an attachment here for people to see. Here's what we see when we try to look at it:

Can I get details on the location of the wire you found loose? I have a 2002 the same problem, I replace the entire Switch unit $250, good fuse, good relay (under seat), all emergency flashers work, and running lights. Just no turn signals. Is there an additional relay of some sort under the front instrument panel on this year (2002) I cant find a part number for it?

if they do emergency, this switch must be checked, all unused switches often do not touch, they are not worth replacing, they are good, only need to be turned on, maybe with the preparation, DO NOT DISASSEMBLY! FURTHER, IF THE EMERGENCY FLASHERS BLink, this is the O.K. interrupter. write to me /adalbert1981@o2.pl

Can I get details on the location of the wire you found loose? I have a 2002 the same problem, I replace the entire Switch unit $250, good fuse, good relay (under seat), all emergency flashers work, and running lights. Just no turn signals. Is there an additional relay of some sort under the front instrument panel on this year (2002) I cant find a part number for it?

When you push the turn signal switch left or right, a ground is sent from the switch to the turn signal cancel unit in the steering stem. This activates it. It starts looking for pulses from the speed sensor and sends a ground to the flasher relay, activating it. The relay in front of the gauge assembly is the position light relay on the 01-05 bikes and has nothing to do with the turn signals flashing or not. When you turn on the right turn signal, does the right side position light go out in the mirror pod?